Suggested by Sonic Sailor Pluto has her energy attacks which can deal a considerable amount of damage to Solaris. The monster won’t really know what hit it. That said, this would only work if Solaris didn’t have immortality, super speed, and high defenses of its own. When you factor that in then Pluto is the one who will be losing in an instant. She’s not ready to take on an end game Sonic boss like this and even now Solaris is known as one of the strongest Sonic villains of all time. Solaris wins.